Black medical students are a particularly vulnerable population to stressors that may contribute to low retention and less effective care toward underserved patients, such as greater perceived stress and lower feelings of acceptance. From primary grades through enrollment in the most prestigious colleges, Black students who are well qualified academically are vulnerable to a range of racial stressors that adversely affect their well-being and undermine their academic performance. However, there have been very few methodologically rigorous tests of strategies for protecting and promoting the well-being of Black medical students. The study proposed here will address this gap by using an experimental design to, a) test the effect of a self-affirmation intervention, a low-cost and easy-to-implement strategy with proven benefits for Black high school and college students, among two distinct groups of Black medical students-students attending 1) predominately White medical schools (PWS), and 2) historically Black medical colleges (HBMC); b) Examine the relative benefit of the intervention for students attending PWS vs. those attending HBMC; and c) Investigate the extent to which medical school factors and individual differences factors moderate the effect of the intervention. We will use evidence-based and proven recruitment methods, to invite approximately 500 Black students to complete a baseline web-based questionnaire in their 3rd year of medical school, since this is a known high-stress time and students may be especially vulnerable due to increasing exposure to clinical environments and demands. Students will then be randomly assigned within medical school (3 HBMC and a stratified random sample of 50 PWS) to either a self-affirmation intervention or a no-treatment control condition. Intervention effects will be assessed using web-based questionnaires at the end of participants' 4th year of medical school. This study is innovative because it is the first, to our knowledge, 1) to conduct a methodologically rigorous test of strategies for protecting and promoting the well-being of Black medical students, 2) to assess the impact of a self-affirmation intervention on the psychological well-being of Black medical students, and 3) to compare the effects of this intervention on Black medical students in historically Black medical schools to those in institutions in which Blacks have been traditionally underrepresented.